The present invention relates to a printed circuit board for surface mounted electrical components.
Known printed circuit boards (PCBs) for surface mounted electrical components include a plurality of rectangular contact pads provided on the surface upon which the components are to be mounted. The pads are coated with solder paste and the components are bonded to the pads by way of electrical connector portions.
The components commonly comprise an elongate, electrically insulating, e.g. ceramic, body portion in the form of a rectangular bar or cylinder, having electrical connectors such as connector caps at each end. Once the components are mounted on the paste covered pads, the whole structure is heated and the solder paste melts in a so-called "reflow" process. Upon solidification, the solder bonds the electrical connectors to the pads so as to provide the required mechanical and electrical connection between the components and the PCB.
With such known PCBs, each component's body portion may overlie and contact substantial portions of the solder coated pads. During the reflow process, when the solder paste is melting, the solder contacting the electrically insulating body portion may separate from the pads and form one or more solder droplets which solidify at the side of the body of the component. The droplets are separate from the pads and connectors and so do not contribute to the connection of the component to the PCB. If the droplets are not removed from the PCB, they can become dislodged from their position next to the components and can cause short circuits at other locations on the PCB. It has been determined that solder droplets can form adjacent to most of the components on the PCB.
Although it is known to remove the droplets by washing the PCB with a chemical solution, the use of such chemicals is becoming increasingly prohibited, and, moreover, the washing of the PCB represents an additional stage which disadvantageously increases the cost and time involved in mounting the components on the PCB.